In a steering device having a steering lock device, when an ignition key is turned into a lock position and pulled out from the key hole, a lock pin projects toward the axis of the steering shaft. As a result, an end portion of the lock pin engages a key lock hole formed in a key lock collar press-fitted to the outer periphery of the steering shaft so as to fix the steering shaft to the outer column not to allow the steering shaft to rotate.
Existing steering devices having a steering lock device have a separate housing for the steering lock device bolted to a flange section of a column after the housing is positioned by fitting an engaging convex part of the housing in a through hole formed in the column.
In cases where the column is made of an aluminum alloy, however, the strength of the column is small. Therefore, when, in a state where the engaging convex part is fitted in the through hole, the housing is clamped to the flange section using bolts, the clamping force of the bolts is applied to around the through hole possibly causing the column to be cracked. Also, when, in a key-locked state (the lock pin is engaged with the key lock hole) , a large rotating torque is applied to the steering wheel, a bending moment is applied to the lock pin causing a large stress to be applied to around the through hole to possibly crack the column.
In the steering device disclosed in Japanese Unexamined Patent Application Publication No. 2002-337663, a flange section made of thick steel plate is welded to a column made of a steel pipe enhancing the mounting rigidity between the column and the housing for a steering lock device. Also, in the steering device, an engaging convex part of the steering lock device is tightly fitted in a through hole formed in the column, and the bending moment applied to the lock pin in a key-locked state is born by both the flange section and the through hole. The column used in the steering device disclosed in Japanese Unexamined Patent Application Publication No. 2002-337663 is, however, made of steel, and no measure for reducing the stress concentration around the through hole formed in a column made of an aluminum alloy is disclosed.